This review summarizes the progress of pre-lithiation technologies involving the fundamental research and practical application of LICs.

Next‐generation Li‐ion batteries (LIBs) with higher energy density adopt some novel anode materials, which generally have the potential to exhibit higher capacity, superior rate performance as well as better cycling durability than conventional graphite anode, while on the other hand always suffer from larger active lithium loss (ALL) in the first several cycles. During the last two decades, various pre‐lithiation strategies are developed to mitigate the initial ALL by presetting the extra Li sources to effectively improve the first Coulombic efficiency and thus achieve higher energy density as well as better cyclability. In this progress report, the origin of the huge initial ALL of the anode and its effect on the performance of full cells are first illustrated in theory. Then, various pre‐lithiation strategies to resolve these issues are summarized, classified, and compared in detail. Moreover, the research progress of pre‐lithiation strategies for the representative electrochemical systems are carefully reviewed. Finally, the current challenges and future perspectives are particularly analyzed and outlooked. This progress report aims to bring up new insights to reassess the significance of pre‐lithiation strategies and offer a guideline for the research directions tailored for different applications based on the proposed pre‐lithiation strategies summaries and comparisons.

For amorphous ruthenium, the current‐voltage characteristics of cyclic voltammetric (CV) curves depended strongly on the voltage scan rate. At high voltage scan rates, asymmetrical reduction and oxidation current behavior was obtained. The specific capacitance decreased with increasing voltage scan rate. The composite electrode was made by mixing ruthenium oxide powders and activated carbon black. The CV curve symmetry improved significantly at high voltage scan rates using composite electrodes, and the specific capacitance was less sensitive to the voltage scan rate. An electrochemical capacitor made with ruthenium oxide‐carbon composite electrodes demonstrated current densities as high as . ©1999 The Electrochemical Society

Li–air cells based on Li foil as an anode electrode, freestanding carbon nanotube/nanofiber mixed buckypaper as an air (cathode) electrode, and organic electrolyte were assembled. The air electrode was made with single-wall carbon nanotube (SWNT) and carbon nanofiber (CNF) without any binder. The discharge capacity was strongly dependent on both the discharge current density and the thickness of the air electrode. A discharge capacity as high as 2500 mAh/g was obtained for an air electrode at a thickness of <mml:math display="inline"><mml:mrow><mml:mn>20</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi></mml:mrow></mml:math>20μm with a discharge current density of <mml:math display="inline"><mml:mrow><mml:mn>0.1</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mtext>mA</mml:mtext><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>0.1mA/cm2 ; however, it was reduced to 400 mAh/g when the thickness of the air electrode was increased to <mml:math display="inline"><mml:mrow><mml:mn>220</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi></mml:mrow></mml:math>220μm . For a <mml:math display="inline"><mml:mrow><mml:mn>66</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi></mml:mrow></mml:math>66μm thick air electrode, the discharge capacity decreased from 1600 to 340 mAh/g when the discharge current density increased from 0.1 to <mml:math display="inline"><mml:mrow><mml:mn>0.5</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mtext>mA</mml:mtext><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>0.5mA/cm2 . The scanning electron microscope images on surfaces of the air electrode from a fully discharged cell showed that the voids at the air side were almost fully filled by the solid deposition; however, the voids at the membrane side were still wide open.

A model for predication of the gravimetric and volumetric energy densities of Li-air batteries using aqueous electrolytes is developed. The theoretical gravimetric/volumetric capacities and energy densities are calculated based on the minimum weight of the electrolyte and volume of air electrode needed for completion of the electrochemical reaction with Li metal as an anode electrode. It was determined that both theoretical gravimetric/volumetric capacities and energy densities are dependent on the porosity of the air electrode. For instance, at a porosity of 70%, the maximum theoretical cell capacities are <mml:math display="inline"><mml:mrow><mml:mn>435</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mAh</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow></mml:math>435mAh∕g and <mml:math display="inline"><mml:mrow><mml:mn>509</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mAh</mml:mi><mml:mo>∕</mml:mo><mml:msup><mml:mi>cm</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>509mAh∕cm3 in basic electrolyte, and <mml:math display="inline"><mml:mrow><mml:mn>378</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mAh</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow></mml:math>378mAh∕g and <mml:math display="inline"><mml:mrow><mml:mn>452</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mAh</mml:mi><mml:mo>∕</mml:mo><mml:msup><mml:mi>cm</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>452mAh∕cm3 in acidic electrolyte. The maximum theoretical cell energy densities are <mml:math display="inline"><mml:mrow><mml:mn>1300</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>Wh</mml:mi><mml:mo>∕</mml:mo><mml:mi>kg</mml:mi></mml:mrow></mml:math>1300Wh∕kg and <mml:math display="inline"><mml:mrow><mml:mn>1520</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>Wh</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">L</mml:mi></mml:mrow></mml:math>1520Wh∕L in basic electrolyte, and <mml:math display="inline"><mml:mrow><mml:mn>1400</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>Wh</mml:mi><mml:mo>∕</mml:mo><mml:mi>kg</mml:mi></mml:mrow></mml:math>1400Wh∕kg and <mml:math display="inline"><mml:mrow><mml:mn>1680</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>Wh</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">L</mml:mi></mml:mrow></mml:math>1680Wh∕L in acidic electrolyte. The significant deduction of cell capacity from specific capacity of Li metal is due to the bulky weight requirement from the electrolyte and air electrode materials. In contrast, the Li-air battery using a nonaqueous electrolyte does not consume electrolyte during the discharge process and has high cell energy density. For Li-air batteries using both aqueous and nonaqueous electrolytes, the weight increases by 8–13% and the volume decreases by 8–20% after the cell is fully discharged.